Monday, March 21, 2011

Eric Fossum published his recent presentation of Quanta Image Sensor at Yale University - a nice presentation summarizing today's state of the art and proposing a future direction. Two slides explaining the concept:

There is also Eric's comment at dpReview forums talking about the possible future developments:

"So, for now, you can just count on incremental progress. The progress is still pretty rapid so even incremental progress over a few years looks like giant strides forward. The CMOS APS is probably good for a 100Mpixels at the consumer level, maybe more, with the usual trade off between pixel SNR, DR, and resolution effects on IQ. WDR(HDR, XDR) and global shutter functions may appear in the next few years in DSLRs. Fast frame readout opens the door for lots of fun post processing.

I do expect to see some 3D capability inserted down the road as there is already research going on for RGBZ kernels (one pixel used for range finding). This is challenging and product development will depend on consumer pull. I don't expect much pull from this community but for better or worse, this community has never had much impact on sensor technology development compared to consumers at large."

14 comments:

This was a surprise to find this posted here, and so quickly. I guess I have to commend ISW on his information gathering skills!

Meanwhile, the quote above, referring to current CMOS APS technology as seen by the DSLR user community, was preceded with the following comment regarding the QIS ("quiz") concept which I think it is important to mention:

"The QIS is a revolutionary step and sometimes revolutions don't succeed. There are certain advantages to the QIS concept but I am not sure they are compelling at this time. Besides, QIS implementation is a good 5 years+ away and maybe something better will come along or maybe the CMOS APS will have progressed so far that there is no remaining advantages of the QIS.

The QIS puts the image formation process into the digital domain so that pixel boundaries (X,Y, t) can be arbitrarily adjusted, retroactively if need be. Also, motion tracking by XY shift and digital integration can be more readily performed. The digital film algorithm, previously discussed is one way the QIS would be applicable to photography by returning grain concepts and D log H exposure properties."

Eric's description of QIS seem to be a good fit to the generic work undertaken in compressive sensing. In particular, I noted that the timebits planes were likely sparse (a condition for using compressive sensing). The track and sum process can be improved by a CS acquisition process. I noted specifically on slide 23, the statement that "Not really feasible at this time to consider 5.3 Tb/s data rate off chip". I agree but if the compression a la CS is done on the chip, you might get this number down.

Pierre Vandergheynst et al came out recently with one type of implementation of the concept of using CS on an imaging chip ( A (256x256) Pixel 76.7mW CMOS Imager/ Compressor Based on Real-Time In-Pixel Compressive Sensing, Vahid Majidzadeh, Laurent Jacques∗ , Alexandre Schmid, Pierre Vandergheynst and Yusuf Leblebici, available at: http://goo.gl/2WZWt)

For those of you looking for a layman's introduction to CS, here is my recent attempt at answering this question on Quora: http://goo.gl/qGfw5

Igor - I will check it out. Thanks.Albert - That is a trick question! I don't see you retiring for a long time. But generally the QIS is a long way out.

It is possible that QIS is actually the endpoint of CMOS APS evolution. This may become true if we can let go of YNSR10 and DR issues in individual pixels and frames and instead start summing many faster frames to generate a single image as normal method of image capture.

can use a regular imager this way and make it worse or apparently better by spec if pixel is the processed as combination of many. This is not different because the unit is brought to one electron. I hope good research money or grad student time is not spent frivolously.

The prior art are the myriad of 1-bit A/D and D/A circuits built on delta-modulation and sigma-delta modulation. The notion that you need to use a large full-well and fixed time-domain sampler for counting PD electrons is very last century. Pixels are perfectly amendable to continuous sampling if the rest of the circuit can keep up. The advantage of this kind of design is that you can use the same strategies from the prior work to eliminate noise.